The present invention relates to ultrasound imaging systems and, more particularly, to a method and apparatus for controlling rotation of an ultrasound transducer.
The users of medical ultrasound transducer probes, hereinafter referred to as sonographers, can obtain images of a region within a body by properly positioning a probe against the body. In order to obtain images having diagnostic value, the sonographer may have to physically manipulate the position of the probe by sliding, rotating, and tilting the probe. One area in particular where this manipulation is more challenging is transesophageal cardiac imaging. During transesophageal cardiac imaging, the sonographer positions a transducer housing at the tip of the probe against the esophagus or stomach of a patient to obtain different fields of view of the heart.
For this application, the transducer housing typically contains a number of acoustic transducer elements, which may be sequentially electrically excited by an ultrasound control and operating system to obtain an image in an object plane that is perpendicular to the transducer housing and the transducer elements.
It has been found desirable to rotate the transducer elements contained within the transducer housing independently from the physical manipulation of the housing itself. In combination with the ability to slide, rotate and tilt the transducer housing, the ability to independently rotate the transducer elements within the housing gives the sonographer the ability to obtain an ultrasound image of any or all object planes orthogonal to the upper surface of the transducer elements at each location to which the housing can be moved.
Devices that allow the sonographer to rotate the transducer elements independently from the transducer housing are known. For example, U.S. Pat. No. 5,402,793 to Gruner et al. shows an ultrasonic transesophageal probe for the imaging and diagnosis of multiple scan planes. The probe includes two buttons that respectively control the clockwise and counter-clockwise rotation of the transducer at the tip of the probe. Each of the buttons is a three-position switch: off, slow rotation and fast rotation. The states of the switches are transmitted to the ultrasound system, interpreted and converted to motor drive signals.
A disadvantage of this device is that it does not provide for automatic control of the ultrasound transducer during imaging. It has been found desirable to perform ultrasound examinations in which the ultrasound transducer is stepped through a predetermined sequence of rotary positions. It has also been found desirable to obtain images while the ultrasound transducer is rotating at a fixed rate. Accordingly, it would be desirable to have an improved method and apparatus for remotely controlling rotation of the ultrasound transducer.